Machine knife



Ju ne 29, 1937. c, E, G AFF 2,084,993

MACHINE KNIFE Filed March 22, 1935 3o 32 23 I INVENTOR 24 26 25 CHARLES E'GAFE 74 BY F 12 WWW V ATTORNEYS Patented June 29, 1937 STE Application March 22,

4 Claims.

This invention relates to improvements in machine knives, particularly for use in cutting paper and similar sheet stock, and has for a principal object the provision of an extension which may be-applied to the knife after it has become too short for use due to repeated sharpenings, thereby increasing the life of the knife.

In machine knives the knife bars, to which the knives are secured, each have a surface against t which the back edge of the knife members, and

another surface at right angles to said first surface, and against which the face of the knife contacts when the knife is secured thereto. The

knife is secured to the knife bar by means of In" bolts passing through the knife bar and engaging threaded holes in the knife. Usually the surface in the vicinity of the bolt holes in the knife bar is under-cut or relieved so that the knife may be tightly clamped against the knife 50* bar in parallel relation to the surface of the knife bar.

The'knife, due to repeated grindings, eventually becomes too short for use. As the knife still contains good cutting steel, it is poor economy to gg throwit away when it reaches this state. In devices of the prior art the life of these knives has been extended in two ways: (a) by providing the knife bar with screws bearing against the back or blunt edge of the knife; and (b) by screwing or pinning an extension on to the back orblunt edge of the knife.

The first of these methods has the distinct disadvantage in that when the knife is bolted to the knife bar, and the bolts are tightened, the blunt 35 edge of the knife is forced into the undercut portion of the surface of the knife bar with the result that the knife is cocked. The second of these methods gives a similar result due to the fact that strains, due to the clamping action of 4b" the bolts, are imparted to the screws or pins and the blunt 'edge of the knife is forced into the under-cut portion of the knife bar and out of parallel relation to the surface of the knife bar. N This second method is shown and described in 45 Patent No. 596,530 issued on January 4th, 1898 to Thomas F. McCoy.

A further object of the present invention is the provision of an extension bar so formed that it may be easily applied to my new and improved mach'ine knife after the latter has become too short due to repeated sharpenings, and securing the knife andthe extension bar together in such relation that regardless of the position of .the under cut portion of the knife bar about the bolt holes in the latter, the knife and extension 1935, Serial No. 12,423

assembly is practically as rigid as the knife was originally and will maintain its perfect perpendicular position when clamped in parallel relation to the knife bar.

Machine knives like any other articles made of tempered steels have various internal stresses and strains. As the knives are ground away due to repeated sharpenings these stresses effect warping in the knife thereby making it more or less difficult to apply an extension bar thereto or to remove the same therefrom, and due to the small amount of space between the knife bar and the paper clamping member, it is difficult to insert a warped blade therebetween.

Another object of the invention is the provision of a novel method of applying extension bars to machine knives and/or removing extension bars therefrom, wherein an extension bar, when applied to the knife, becomes, in effect, a knife holder.

Other objects and advantages will become ap parent to those skilled in the art.

Referring to the drawing:

Figure l is an elevation of a knife constructed according to a preferred form of the invention and which, due to repeated grindings, is too short to be used in a machine;

Figure 2 is an elevation of a portion of an extension bar adapted to be used with the knife shown in Figure 1;

Figure 3 is a sectional elevation of the knife taken along the line 3--3 of Figure 1;

Figure 4 is a sectional elevation of the extension bar taken along the line lt in Figure 2;

Figure 5 is a sectional elevation of the knife taken along the line 55 of Figure 1;

Figure 6 is a sectional elevation of the extension bar taken along the line E-6 of Figure 2;

Figure '7 is a fragmentary view of an assembly of the knife shown in Figure l and the extension bar shown in Figure 2;

Figure 8 is a sectional elevation of the knife and extension bar assembly taken along the line 8--B of Figure 7;

Figure 9 is a sectional elevation of the assembly taken along the line 99 of Figure 7;

Figure 10 is a side elevation of a threaded bushing which is included between the knife and the knife bar thereby providing a further means for clamping the assembly to the knife bar of a machine;

Figure 11 is an isometric view of the device shown in Figure 10;

Figure 12 is a sectional elevation of a typical knife bar with a machine knife secured thereto; and

Figure 13 shows a jig for assembling the knife and the extension bar.

The typical knife bar of a machine is shown in Figure 12 and designated by the numeral 20'. This knife bar has a surface 2! which moves in a parallel line when the knife bar, in its normal position in the machine, is actuated. The knife bar also has a surface 22 which is substantially at right angles to the surface 2|.

The knife bar is provided with a plurality of bolt holes, one of which is shown and designated by the numeral 23. The hole 23 has a counterbored portion 24 which is of sufficient size to provide clearance for the bolts, one of which is designated by the numeral 25, and washers 26.

The knife, generally designated by the numeral 21, is usually made of wrought iron or lower grades of steel and has applied thereto by welding or any other suitable manner a portion 28 of high grade steel which is tempered and capable of maintaining a sharp cutting edge. The knife also has a beveled portion 29 forming a surface along which grinding is effected.

The front surface 30 of the knife is ground true and is the surface which engages and aligns precisely with the surface 2! of the knife bar. In order that this alignment may be maintained as precisely as possible it is customary with most of the machine manufacturers to under-cut the surface of the knife bar along a longitudinal zone about the bolt hole 23 thereby forming a depression 3! in the surface 2! of the knife bar.

The blunt or back edge of the knife (the edge opposite to the cutting edge) at its junction with the surface 333 is provided with a chamfer 32, thereby eliminating a square corner, forming a distinct bevelled edge, making it possible to force the knife in under the bottom edge of the knife bar 23 when the knife has become warped as deknife grows shorter due to repeated sharpenings they may be lowered in the knife bar so that the bolts 25 which engage normally the holes 33-3311 are allowed to engage the holes 34.34a. In this, position the portion of the knife extending below the knife bar is lengthened.

. As the knife becomes still shorter it may be lowered to the point where the bolts 25 engage the holes 35-35% At this stage the chamfered corner 32 of the knife 2? is pulled into the depression 3! by the bolts 25 when they are tightened, thereby cocking the knife out of parallel relative to the surface 2!. This causes the knife to mutilate the work and to strike other portions of the machine adjacent to the knife, resulting in scarring said portions and dulling the knife.

When the knife is so shortethat it is necessary to use the holes 35-35a the effect immediately above described is eliminated by the addition to the knife of an extension bar such as that shown in Figure 2 and designated by the numeral 36. This extension bar is of substantially the same thickness as that of the knife. Theextension bar is provided with a plurality of sector shaped tongues each having a hole 38 formed'therein.

The number of these tongues used varies with the length of the knife.

The knife 21a is provided with sector shaped or curvilinear depressions 39 which are similar in shape to the tongues 31. These depressions are of such width that the tongues 31 form a press fit therein.

In the portion of the knife in which the depression 39 is formed, a tapped hole 40 is provided in such position that when the. tongue 31 is in position in the depression 39 this tapped hole is in line with the hole 38. The knife is also provided with a hole 4! concentric with the hole 46 and forming a fit with a screw head such as the screw 42 shown in Figure 8. Figure 8 shows the knife and knife bar assembled with the tongue 3'! in position in the depression 39 and a screw 42 retaining them in this relation.

When assembled the head of the screw 42 should be a few thousandths of an inch below the surface 30a of the knife and forms a dowel fitting both the hole 38in the tongue 31 and the hole 4! in the knife. 7

The extension bar 36 has a plurality of semicircular depressions 43 milled therein and a pluralty of other semi-circular depressions 44 in stepped relation to and concentric with the depressions 43. Matching these semi-circular depressions, when the tongue 37 is in position in when the extension bar and knife are assembled the holes 41 and 48 are oppositely disposed,

A bushing 49 is provided with a threaded hole 53, of the same pitch and number of threads as that of the bolt 25. has a portion of the same thickness and diameter of that of the depressions 44 and 46. The bushing 49 also has a reduced portion 52 of a diameter and length equal to the depressions 43 and 45. The bushing 49 is provided with pins 53 and 54 which engage the holes 4! and 48 respectively when the knife and the extension bar are assembled as shown in Figure 9.

When assembled in the manner just'described. the threaded. hole 50 is substantially in line with the hole 34a in the knife.

The extension is also provided. with a plurality of tapped holes 55 the purpose of which Will presently be described.

When the extension 36 is applied to a worn knife Ela its length is increased so that the upper hole 35 and the new added hole 53 may be used for lowering the knife as it is ground away by repeated sharpenings.

As pointed out above, stresses and strains withi in the metal forming the knife are relieved to some extent by repeated grindings and result in warping the knife itself. This being the case the depressions 33 formed in the knife, due to this warpage, will not all be in line with each is illustrated in Figure 13 was devised for applying extension bars to and/or removing them from knives.

The outside of the bushing BIL 7 A pair of old knives 56 and 51 are utilized. A plurality of members, generally designated by the numeral 58, are secured to these knives.

The members 58 each consist of a block 59 having formed therein a slot 69 in which a metallic' strip 6| is mounted at right angles to the block. The metallic strip 6| is secured to the block 59 by means of screws 62. A screw 63, having threads matching the threaded hole 33b in the knife 56, secures the member 58 to the knife 56 with the metallic strip 6| resting on the blunt end of the knife 56. Before the member 58 is secured to the knife 56 the shank 66 of an eye bolt 64 is screwed into a threaded hole 61 formed in the metallic strip 6|. When the member 58 is secured to the knife as above described a screw passing through the eye of the bolt 64 is utilized for securing the head of the eye bolt to the knife 51; While the screw 65 is being tightened the metallic strip BI is firmly held down against the blunt edge of the knife 51. "The block 59 has formed therein a clearance hole 69 which is of suitable diameter to form a clearance for a screw 10. The screw 18 is of such diameter and has threads of a pitch matching the holes 55 in the extension bar 36. The block 59 is also provided with a second hole H which is tapped to fit the threads of the screw 10. The screw 16 is'also provided with a wing nut.

Normally the nuts 68 are not screwed down onto the metallic strip 6|. They are not placed on the threaded shank 66 of the eye bolts until after the knife 21a is positioned on the fixture as shown in Figure 13.

A plurality of assemblies or members 58 (the number varying in accordance with the length of the knife) is applied to the old knives 56 and 51. The knife 21a to which the extension bar 36 is to be applied is placed upon the assembly 56-5'|--58 .with the threaded tongues 66 of the bolts 64 preferably extending through the holes 34P-34a after which the nuts 68 are applied and tightened down thereby clamping the old knife 51, the metallic strips 6| and the knife 21a rigidly together. As all of the metallic strips 6| are of the same thickness and as the assemblies 58, of which the strips 6| are members, are positioned near together along the surface of the old knives 56 and 51 the warpage in the knife 21a is compensated for.

To apply an extension bar 36 to the knife 21a screws 10 are screwed into the holes H in the various blocks 59 and these screws are turned until they all member up against the edge of the extension bar 36 which had previously been placed in position across the metallic strip 6| with the tongues 31 in cooperative relation to the depressions 39 in the knife.

A bushing 49 is placed in position in each depression 45-46 or 4344 with the pin 53 or 54 in line respectively with the hole 48 or the hole 41. When this has been done the screws 10 may be rotated or turned to force the tongues 31 of the extension bar 36 into engagement with the depressions 39 in the knife. It has been found preferable to progressively advance each screw, bearing along the length of the extension bar, so that the extension bar 36 is moved forward toward the knife in as near a parallel manner as possible.

When the operation has reached the stage where the flat surfaces of the extension bar are in contact with the blunt edge 22a of the knife the tongues 31 are completely within the depressions 39 at which time the holes 38 and 40 coincide with each other and the depressions 43-44 and 4566 completely embrace the bushing 49 with the pin 54 in the'hole 48 and the pin 53 in the hole 41 after which the screws 42 may be inserted in the holes 4| and screwed into the holes 46 thereby securing the knife and the extension bar together and forming a rigid structure. The nuts 68 may then be removed and the knife-extension bar assembly is ready to be applied to the machine.

This invention contemplates the production of knives having, in addition to the holes 3334-35 therein, depressions 39 formed therein and depressions 4546 and the holes 4ll4| and 48 formed therein so that no machine work is necessary on the premises of the customers to apply an extension bar to a knife.

A single extension bar may be used over and over from time to time onvarious worn knives.

To remove an extension bar from a knife the knife-extension bar assembly is placed on the fixture made by the old knives 56 and 51 and members 58 and the nuts 68 are screwed down to tightly clamp the assembly on to the fixture. The screws 76 are then inserted into the holes 69 and screwed into the tapped holes 55 in the extension bar- 36. The screws 42 are then removed from the knife and extension bar assembly after which the wing nuts 12 may be turned to pull the extension bar 36 from the knife 21a thereby making the extension bar 36 available to be applied to other worn knives.

Due to'the rigid structure formed by combining the knife and the extension bar in the manner shown and described herein, as far as clamping the knife to the knife bar 28 of the machine, this assembly is substantially as rigid as a new knife would be and will give the same result as a new knife.

The depression3| in the surface 2| of the knife bar cannot distort the newand improved assembly knife and extension bar.

In some of the machines employing knives, the knifebar is provided witha series of holes, one of which is indicated in dotted lines in Figure I2 and designated by the numeral 14. When the knife becomes too short to use the holes 33-33a the knife is removed from the knife bar and a rectangular strip is affixed to the knife bar by means of screws passing through the holes 74. This strip is of such width that when the knife is positioned against it it may be bolted to the knife bar by bolts engaging the holes 34-34a. When the knife becomes too short to utilize the holes 3434a the knife is removed from the knife bar and a wider strip is substituted for the stripjust described and this latter strip is of such width that when the blunt edge of the knife members up against it the bolts in the knife bar will engage the holes 3535a. In many cases the difficulty encountered is that the chamfered corner 32 in a knife enters the depression 3| in the knife bar and when pressure is applied to the knife by means of the bolts 25 the knife is cooked and does not function in the machine as it should.

Extending the knife by this method is only a make-shift and cannot approximate the results obtained by the new and improved knife-extension bar assembly described herein which forms a rigid structure and in which the surface 73 of the extension bar positively members up with the surface 22 of the knife bar and due to the rigidity of the structure the position of the knife is not distorted due to the presence of the depression 3| in the knife bar.

Although a preferred embodiment of the invention' is herein shown and described it is obvious that many modifications may be made by those skilled in the art without departing from the spirit of the invention asdefined in the following claims.

What is claimed is:

1. A machine knife adapted to be secured to a movable part of said machine, a plurality of mortises formed within saidknife and communieating with one plane surface thereof, an extension bar. having a plurality of tenons extending from one surface thereof adapted to be contained in said mortises when the bar is applied to the knife with said surfaces in contact with each other, tapped holes formedin said knife each communicating with one of said mortises, clearance holes formed in said knife each concentric with one of said tapped holes, a clearance hole formed in each of said tenons concentric with and parallel to said first clearance holes when said tenons are contained in said mortises, and screws extending through said clearance holes and into said tapped holes for securing the knife and the extension bar together to form a rigid structure.

2. A machine knife adapted to besecured to a movable part of said machine, a plurality of key- Ways of the Woodruff type formed in said knife and communicating with one plane surface thereof, an extension bar having a plurality of keys formed integral therewith and extending from one surface thereoflsaid keys being adapted to be contained in said keyways when the bar is applied to. the knife with said surfaces in contact with each other, tapped holes formed in said knife each being transverse to and communicating with one of said .keyways, clearance holes formed in said knife eachbeing concentric with one of said tapped holes, a clearance hole formed in each of said keys transverse thereto, concentric with and parallel to said first 'clearanceholes when said knife and said extension bar are assem bled with said keys positioned in said keyways, and screws having heads forming dowels fitting ings, means forming a plurality of curvilinear grooves disposed along substantially the longitudinal, axis of the knife and terminating in the upper surface thereof, a plurality of curvilinear tongues formed integral with said bar along one surface thereof and adapted to be contained en.-

tirely within said grooves in the mass of the knife I for holding the knife in rigid relation to said extension bar, and screw means cutting atleast two surfacesof said knife within the zone of each of said curvilinear grooves, and passing transversely through said tongues for retaining the knife and the extension bar in fixed relation to each other. r A 4.,As an article of manufacture, a machine knife having a series of tapped holes formed therein for attachment to a movable member of a machine, said knife having a cutting edge, two parallel faces and a blunt edge opposite to said cutting edge and at right angles to said parallel faces, means forming apluralityof semi-circular grooves within the body of said knife and communicating with said blunt edge, holesformed in said knife andextending from one of said faces to the other of said faces through said grooves and having a portion of their lengthsthreaded, an

CHARLES E. G. AFF. 

